Multilayer body with a laser-sensitive layer

ABSTRACT

The present invention relates to a process for increasing the level of safeguard in respect of forgery of paper documents. For that purpose, applied to the paper document is a transfer film or laminating film having a laser-sensitive layer. This multi-layer body is then treated with laser radiation. In that case, a laser-induced marking is produced in the laser-sensitive layer, for example, by laser-induced bleaching, laser-induced color change or laser-induced blackening. Respective individualization of the document can be effected by way of that laser-induced marking.

The invention concerns a multi-layer body comprising a substrate whichat least partially comprises paper material, with a single-layer ormulti-layer structure, based on a transfer film, for example a hotstamping film, or based on a laminating film, or based on printing orcoating in some other fashion, as well as a process for the productionof a laser-induced marking in such a multi-layer body.

The use of laser radiation for producing laser-induced markings forenhancing the level of safeguard against forgery of cards comprisingplastic material such as identity cards, code cards and so forth isknown. Individualization of such cards or the like can be effected withthe laser-induced markings.

Laser treatment for individualization purposes is not used in relationto documents which comprise paper material because paper material burnsunder the effect of laser radiation.

The object of the invention is to increase the level of safeguardagainst forgery of paper documents by the use of laser radiation. Inthat respect the aim is to achieve a specific structural configurationof the paper document and a particular process for increasing the levelof safeguard against forgery.

The invention attains that object with a multi-layer body as set forthin claim 1 and a process as set forth in claim 16.

The solution according to the invention provides that the paper documentis in the form of a multi-layer body in which a single-layer ormulti-layer film or the like, for example a hot stamping film, isapplied to the substrate comprising paper material. The layer structureproduced in that way should have at least one layer containinglaser-sensitive material. The laser-sensitive material is such that alaser-induced marking, for example in the form of a color marking or inthe form of a black marking, is converted by laser action on the filmapplied to the substrate, in the laser-sensitive layer. Surprisingly,upon laser irradiation, under the effect of the radiation on the filmapplied to the substrate, the substrate comprising paper material is notdamaged, that is to say burning of the paper material which occurs whenpaper material is irradiated directly under the effect of the laser doesnot take place.

In preferred embodiments however for the sake of certainty arrangedbetween the laser-sensitive layer and the surface of the substrate thereis also a special background layer which reflects the laser radiationused in the laser treatment to a high degree and preferably absorbs thenon-reflected component of the laser radiation or at least at any eventdoes not allow it to pass through to the subjacent layers and thereforenot to the surface of the substrate. By virtue of its light reflectionthat protective background layer can additionally also act as abrightening means or color booster in respect of the laser-inducedmarking produced in the laser-sensitive layer. In preferred embodimentsthat background layer which has both a protective action and also abrightening and color-boosting action is arranged under thelaser-sensitive layer exclusively in the region in which thelaser-induced marking is produced.

The background layer can also be transparent in relation to light in thevisible spectral range but at the same time non-transparent for laserradiation in a given wavelength range, for example for the wavelengthrange which is used when producing the laser-induced marking. If afurther laser-sensitive layer is arranged under the background layer, itis advantageous if the background layer is transparent in relation tothe laser radiation which is used for producing the laser-inducedmarking in that layer.

In particularly preferred embodiments, it is provided that thelaser-sensitive material has at least one coloring agent which isbleachable by the laser action or which changes its color by the laseraction with a color change. In this respect the laser-sensitive materialcan advantageously be in the form of a coloring agent mixture which iscomposed of a plurality of differing coloring agent components. Amulti-color image with a wide variation in the colors which can beproduced by a laser-induced procedure is possible with embodiments inwhich the laser-sensitive material is in the form of a mixture of atleast two laser-sensitive components, in respect of which it appliesthat, under the laser conditions which are specific for one component,the other component is not variable or not substantially variable.

Particularly preferred embodiments are those in which a full-color imagecan be produced in a laser-induced procedure. It is provided in thoseembodiments that the laser-sensitive material is a mixture of at leastthree components, wherein each of those components is respectively acoloring agent, for example a pigment or another coloring agent. Thepigments are mostly insoluble, preferably inorganic coloring agents.Other coloring agents are for example organic coloring agents. These aregenerally soluble. It is possible to use mixtures which as coloringagents have exclusively pigments or exclusively other coloring agents orpigments and other coloring agents. The coloring agents which thereforeform the components of the mixture are referred to hereinafter for thesake of brevity as components. It is essential that one or more of thecomponents can be bleached by means of laser under laser conditionswhich are respectively specific for the component involved. In otherwords, for bleaching the first component, there is a first lasercondition, for example a first specific laser wavelength; for bleachingthe second component there is a second laser condition, for example asecond specific laser wavelength, and for bleaching the third componentthere is a third laser condition, for example a third specific laserwavelength. Those specific laser conditions or laser wavelengths usedfor bleaching the various components are respectively different fromeach other. They are also so selected that, under the respectivespecific laser conditions for a component, for example the specificlaser wavelength, only that one component or preferably only that onecomponent can be bleached and in that procedure the other componentscannot be bleached or substantially cannot be bleached. In that way itis possible for only one respective component to be specificallybleached in a step in the laser treatment, while the others are leftunaltered.

If a three-component mixture is used, the color of the marking istherefore formed prior to the first step by the three components. Afterthe laser treatment of the first step the color of the marking at thetreated location is formed by the two components which have not beenbleached in the laser treatment of the first step and possiblyadditionally by the residual color of the component which was bleachedto a greater or lesser degree in the first step, depending on therespective treatment involved. Preferably, the coloring effect isproduced by subtractive mixing of the components which are present mixedin the laser induced layer. The various components can be present in alayer mixed in closely juxtaposed relationship or mixed in a multi-layermutually superposed relationship.

The process for the production of a multi-color image provides that in afirst step only the one component is bleached by laser irradiation of alocation of the body, that is the laser-sensitive layer, under laserconditions which are specific for one of the for example (three)components, and that in a second step by laser irradiation at the samelocation of the body, under laser conditions which are specific for afurther one of the (three) components, only that further component isbleached. In the first step therefore, besides the bleached firstcomponent, there still remain the other (two) unbleached components, sothat the color is accordingly formed by those (two) unbleachedcomponents, possibly with an incomplete degree of bleaching of the firstcomponent in addition with the residual color of the first componentwhich is only bleached to a greater or lesser degree. After the secondstep in which the second component is bleached there is still only onecomponent remaining—if a three-component mixture was originally used—sothat then therefore the color is formed only by that remainingcomponent. That applies for the situation where the other componentshave been completely bleached in the preceding steps. Otherwise, that isto say with an incomplete degree of bleaching of the first component inthe first step and with an incomplete degree of bleaching of the secondcomponent in the second step, the color after the second step isadditionally formed by the residual color of the first and secondcomponents which were only bleached to a greater or lesser degree in thefirst and second steps.

In addition, provided as an optional third step is the laser treatmentof the same location on the body for the third component, that is to saythe component which has not previously been bleached, wherein only thatthird component is bleached at the same location of the body under laserconditions which are specific for that third component, for example aspecific laser wavelength. After that third step therefore at thelocation in question, all three components have been bleached or havebeen bleached more or less, according to the respective degree ofbleaching. Therefore, depending on a possible colored background layeror also possible further components in the body or in the same layer ofthe body, the above-mentioned location of the body appears colorless ortinted, and in the limit case it appears white when the background iswhite.

There are also possible further steps, in each of which one or morerespective further components is or are bleached, under specific laserconditions. It is preferably provided that in general, in an n-th step,by laser irradiation of the same location of the body, for anotherfurther one of n components, only that n-th component is bleached.

Depending on the respective choice of the components and the specificlaser conditions it can also be provided that at least one of thecomponents exhibits a color change in the laser irradiation procedure.

In the laser treatment in the individual steps, it is respectivelyprovided that the color change or degree of bleaching to be achieved isadjusted in the laser irradiation procedure by control of the laserconditions, in particular the laser wavelength, the laser intensityand/or the irradiation time.

The laser conditions used in the respective individual steps arepreferably experimentally ascertained and/or optimised before carryingout the process, by way of tests with the individual components. Thecriterion in regard to the choice of the laser conditions is preferablythe bleaching result to be achieved. The choice of the laser conditionswhich are used in relation to the individual steps can be such that thecomponent absorbs light at the wavelength of the laser light used forthe bleaching operation, insofar as the component at that wavelength hasan absorption maximum, preferably one of a plurality of absorptionmaxima, or preferably its sole or its greatest absorption maximum.However the choice can also be such that the component absorbs light atthe laser light wavelength used for the bleaching operation, but in thatcase at that wavelength the component does not have an absorptionmaximum, but rather that wavelength is outside the absorption maximum oroutside the absorption maxima of the component.

In order to be able to operate with a pigment mixture with relativelyfew pigment components but in that case to be able to produce as manycolors as possible and preferably all colors, it is advantageous if acomponent is a cyan pigment and/or a component is a magenta pigmentand/or a component is a yellow pigment. Preferably the pigment mixturecontains a cyan pigment, a magenta pigment and a yellow pigment. Inparticular embodiments the pigment mixture involves a mixture withexclusively three pigment components, preferably cyan pigment, magentapigment and yellow pigment. All colors can be produced with those threecolors by subtractive mixing. By specific bleaching of the individualpigment components in the individual steps, it is possible for exampleto produce blue in the first step if in that first step only orpreferably only the yellow pigment component is bleached, or in thefirst step it is possible to produce green if in that first step only orpreferably only the magenta pigment component is bleached or in thefirst step it is possible to produce red if in that first step only orpreferably only the cyan pigment component is bleached. Then, the colorcyan, magenta or yellow can be produced in the second step, insofar as afurther one of the remaining pigment components which were not bleachedin the first step is bleached, that is to say if blue has been producedin the first step and therefore cyan and magenta have not been bleachedin the first step, the color cyan can be produced in the second step bybleaching the magenta component in the second step. Production of theother colors is effected in a corresponding manner, for the followingapplies in regard to subtractive color mixing: a) cyan + magenta +yellow black b) cyan + magenta blue c) cyan + yellow green d) yellow +magenta red

The color mixture a) is present prior to the laser treatment, that is tosay prior to the first step. The laser-sensitive layer appears black orgray. The color mixture b) or c) or d) is present after the first step,that is to say at the location at which the laser treatment was effectedin the first step the laser-sensitive layer has a blue or a green or ared color marking respectively. After the second step, when thus lasertreatment of the second step has been carried out in the second step atthe same location, the color marking at that location of the layer is inthe color cyan or yellow or magenta, depending on which of the twopigment components which were not bleached at that location in the firststep have not been bleached in the second step. In order to obtain acolorless or transparent marking in the third step at that location, thethird step is then to be carried out at the same location, in whichthird step therefore the remaining pigment which has not yet beenbleached is now bleached with the respective pigment-specific laserconditions.

In that way a respective color marking of any desired color can berespectively produced at each location by successive laser treatment atthat same location. It is possible in that way for mutually juxtaposedlocations of the body to be successively treated, thereby to produce amulti-color image, preferably a so-called full-color image, on theplastic body by means of mutually juxtaposed color markings.

Instead of the above-described pigment mixture with the pigmentcomponents cyan pigment, magenta pigment and yellow pigment, it is alsopossible to use a corresponding coloring agent mixture with coloringagents which do not represent pigments, that is to say a coloring agentmixture comprising cyan coloring agent, magenta coloring agent andyellow coloring agent as the components involved. In this respectoperation can be implemented in the same manner, the laser conditionswhich are specific for the respective coloring agent being used in theindividual steps.

The various systems preferably use pulsed, frequency-multipliedsolid-state lasers, optical parametric oscillators (OPOs) and pulsed UVlasers (for example Excimer lasers) for the laser treatment. In thelaser treatment the intensity and/or the pulse duration of the laserradiation is preferably so set that a maximum bleaching result or amaximum color change occurs without perceptible damage to the materialof the body. The process can be used on the film applied to thesubstrate and also on separate films alone; thus for example transferfilms, in particular hot stamping films, or on laminating films. The usethereof on transfer or laminating films affords advantages in that thosefilms can also be applied to other substrates which in themselves arevery laser-sensitive in order to decorate or identify them. The filmsrequire only a small amount of coloring agent or pigment as the coloringagents or pigments then only have to be present in a thin layer. Whenusing films it is also possible for bodies of any size, for example verylarge-area paper bodies or the like, to be coated-only locally, forexample by printing processes.

The laser treatment involves using energy densities of preferablybetween 0.05 and 0.5 J per cm² with a pulse duration of between 5 and 20ns, wherein the bleaching result can also be determined by the number ofpulses. The laser-sensitive layer with the pigment mixture can bepresent on the transfer or laminating foil over the full surfacethereof, but also only in region-wise manner.

Preferred embodiments by way of example are described in greater detailhereinafter with reference to the accompanying Figures in which:

FIGS. 1 through 5 show sectional views of various hot stamping filmseach with a laser-sensitive layer,

FIGS. 6 through 10 show sectional views of various laminating films eachwith a laser-sensitive layer,

FIGS. 11 a+11 b show a plan view and a sectional view of an embodimentof a multi-layer body comprising a substrate formed from paper materialwith a transfer film applied thereto with a laser-sensitive layer,

FIGS. 12 a+12 b show a plan view and a sectional view corresponding toFIGS. 11 a and 11 b of a modified embodiment, and

FIGS. 13 through 15 show exploded views of laminated cards comprisingvarious overlay films and inlets comprising paper material.

The films shown in FIGS. 1 through 5 are hot stamping films. The hotstamping film in FIG. 1 includes a carrier film 1, a release layer 2, aprotective layer 3, a laser-sensitive layer 4, a background layer 5 andan adhesive layer 6.

The carrier film 1 is preferably a polyester film of a thickness ofbetween 6 and 100 μm, preferably a thickness of between 19 and 38 μm.The layers 2 through 6 are arranged in superposed relationship on thecarrier film 1. They are applied using per se known processes inproduction of the hot stamping film.

The release layer 2 is a separation layer. It is preferably in the formof a layer which becomes soft when subjected to the action of heat andwhich, when the hot stamping film is applied to the substrate, permitsrelease of the other layers from the carrier film 1. The release layer 2is generally of a thickness of at most 1 μm.

The protective layer 3 is in the form of a protective lacquer layer.This involves a transparent lacquer layer, the purpose of which is tosubstantially protect the free surface of the article decorated with thehot stamping film from mechanical damage and chemical effects. Thethickness of the layer is preferably between 1 and 2 μm.

The laser-sensitive layer 4 is in the form of the so-called first colorlacquer layer. This involves a lacquer layer of a thickness ofpreferably between 3 and 10 μm, which is colored by pigments or othercoloring agents. The pigments or the other coloring systems or coloringagents of this color lacquer layer can be selectively bleached and/orcan be changed in color by color change by means of a laser beam whosewavelength is preferably in the visible range. Preferably the pigmentconcentration of the lacquer layer 4 is between 3 and 15% with respectto solids. The binding agent system of that lacquer layer 4 may not bealtered optically by the action of the laser so that, at the irradiatedlocations, the result is only a colored contrast marking withoutperceptible damage to the film. The film is not perceptibly damagedeither at the surface or in the interior.

The background layer 5 is in the form of the so-called second colorlacquer layer. This layer is colored differently from thelaser-sensitive layer 4. The layer 5 is for example white or of an ivorycolor if the laser-sensitive layer 4 is black or gray. The layer 5serves primarily as a light backup layer for the colors produced in thelaser-sensitive layer 4 by laser radiation. The thickness of the layer 5is preferably between 5 and 20 μm or 15 and 20 μm.

It is possible that the background layer 5—just like the laser-sensitivelayer 4—is not provided over the entire surface area of the hot stampingfoil and thus not over the entire surface to be decorated, in the samecoloration. On the contrary the layers 4 and 5 can be composedindividually—and thus also differently—of regions of different colors.

The adhesive layer 6 involves an adhesive layer which is per se usualand known in relation to transfer films, of a thickness of between about1 and 10 μm, wherein the adhesive layer for a hot stamping film is ofsuch a composition that it becomes sticky only when subjected to thecorresponding action of heat.

The layers 2 through 6 can be produced in accordance with the followingcompositions: Release layer 2 (separation layer): Toluene 99.5 partsEster wax (dropping point 90° C.) 0.5 part Protective layer 3(protective lacquer layer): Methylethylketone 61.0 parts Diacetonealcohol 9.0 parts Methylmethacrylate (Tg = 122° C.) 18.0 partsPolyethylene dispersion (23% in xylene) 7.5 parts (softening point 140°C.) High-molecular dispersing additive (40%, amino 0.5 part number 20)Extender (aluminum silicate) 4.0 parts Laser-sensitive layer 4 (firstcolor lacquer layer): Methylethylketone 34.0 parts Toluene 26.0 partsEthylacetate 13.0 parts Cellulose nitrate (low viscosity, 65% inalcohol) 20.0 parts Linear polyurethane (m.p. > 200° C.) 3.5 partsHigh-molecular dispersing additive (40%, amino 2.0 parts number 20)e.g.: Pigment Blue 15:4 0.5 part Pigment Red 57:1 0.5 part PigmentYellow 155 0.5 part Background layer 5 (second color lacquer layer):Methylethylketone 40.0 parts Toluene 22.0 parts Ethylene vinylacetateterpolymer (m.p. = 60° C.) 2.5 parts Polyvinylchloride (Tg: 89° C.) 5.5parts Polyvinylchloride (Tg: 40° C.) 3.0 parts Dispersing additive (50%,acid number 51) 1.0 part Titanium dioxide (d = 3.8-4.2 g/cm³) 26.0 partsAdhesive layer 6: Methylethylketone 55 parts Toluene 12.5 parts Ethanol3.5 parts Polyvinylacetate (softening point: 80° C.) 6.0 partsButyl/methylmethacrylate (Tg: 80° C.) 8.0 parts Ethylmethacrylate resin(Tg: 63° C.) 3.0 parts Methacrylate copolymer (Tg: 80° C.) 5.0 partsUnsaturated polyester resin (softening point 103° C.) 3.5 parts Silicondioxide 3.5 parts

Instead of that hot stamping film it is also possible to use anothertransfer film. It can be of a corresponding structure to the describedhot stamping film.

Transfer films—in the specific case here hot stamping films—arepreferably applied in a conventional manner to a substrate consisting ofpaper material, for example one or more inlet films of laminated bodies,and more specifically in such a way that the adhesive layer 6 facestowards the substrate surface. In the hot stamping operation theadhesive layer 6 then forms an adhesive bond to the surface of thesubstrate. The carrier film 1 is then pulled off—after softening of therelease layer 2 under the effect of heat in the hot stamping operation.With the hot stamping film applied to the surface of the substrate inthat way the protective layer 3 then forms the upper surface of thestamping film, which is remote from the substrate.

The transfer film shown in FIG. 1 a which in particular can be in theform of a hot stamping film does not have a background layer 5, unlikethe film in FIG. 1.

The hot stamping films shown in FIGS. 2 through 4 have a backgroundlayer which is of a different nature from the film shown in FIG. 1. Inthe example shown in FIG. 2 the background layer is in the form of areflection layer 5 r. In a special case the reflection layer is in theform of a metallic reflection layer. The reflection layer can betransparent or partially transparent for given spectral ranges. It canhave a higher refractive index than the other layers and therefore hasincreased reflection of light. The example shown in FIG. 3 has a layer 5c as an additional lacquer layer which is preferably transparent. Thereis also a reflection layer 5 r which has a diffraction or hologramstructure 5 b in region-wise manner. In the embodiment of FIG. 3 thatstructure 5 b is in the form of a constituent of the lacquer layer 5 cand the adhesive layer 6 as well as the interposed layer. Alternativelyor in addition a diffraction structure can also be provided as aconstituent of the lacquer layer 5 c and/or the laser-sensitive colorlacquer layer 4 and/or the adhesive layer 6. In these cases thediffraction structure can be of a region-wise nature, as illustrated,but it can also be in the form of a continuous layer.

In the example shown in FIG. 4 a printed image 5 d is arranged in thebackground layer 5 c in a defined region and a defined laser-sensitiveregion 4 a is arranged in laterally displaced relationship with theimage in the laser-sensitive layer.

FIG. 5 shows a hot stamping film with a modified layer structure. Thelayer structure is similar to that in FIG. 3, but in this case thesequence of the layers is modified, more specifically in such a way thatthe laser-sensitive layer 4 is arranged on the side of the reflectionlayer 5, which is towards the substrate. The layers are disposed on eachother in the following sequence:

A carrier film 1, a release layer 2, a protective layer 3, anintermediate layer 5 c, a reflection layer 5, a laser-sensitive layer 4,a background layer 7 and an adhesive layer 6. A diffraction structure 5b is provided in the mutually adjoining regions of the laser-sensitivelayer 4, the reflection layer 5 and the intermediate layer 5 c. It canbe in the form of a diffraction grating. Alternatively the structure 5 bcan also be in the form of a hologram structure. In the embodimentillustrated by way of example in FIG. 5 the diffraction structure 5 b isproduced in manufacture of the film, by a procedure whereby thediffraction structure is firstly impressed into the intermediate layer 5c, and then the reflection layer 5 r is applied for example by vapordeposition. The reflection layer 5 is in the form of a smooth reflectionlayer 5 r in the portions outside the diffraction structure. It ispreferably of a layer thickness of <1 μm. It is transparent or partiallytransparent at least for given spectral ranges, at given viewing angles.After application of the reflection layer 5 r the laser-sensitive layer4 is produced. The diffraction structure 5 b produced in that way isformed in the directly mutually adjoining regions of the layers 5 c and4. When the diffraction structure is viewed varying optical effects areproduced in dependence on the lighting and viewing angles.

In the case of the film in FIG. 5 a the layers occur in the followingsequence: carrier layer 1, release layer 2, protective layer 3,laser-sensitive layer 4, reflection layer 5 r, laser-sensitive layer 4,additional lacquer layer 7 and adhesive layer 6. The laser-sensitivelayers 4 which are disposed on both sides of the reflection layer 5 rcan be identical, that is to say the reflection layer is then arrangedin that laser-sensitive overall layer. The laser-sensitive layershowever may also be different. A diffraction structure 5 b is providedin mutually adjoining regions of the laser-sensitive layers 4 and thereflection layer 5 r. Alternatively the structure 5 b may also be in theform of a hologram structure. In this embodiment, enhanced safeguardsagainst forgery are afforded by the fact that two laser-sensitive layersadjoin the diffraction or hologram structure, and they can be the sameor different. In this arrangement the lacquer layer 7 which is optionalis in the form of a transparent layer or a bright backup layer.Alternatively the lacquer layer 7 and the adhesive layer 6 may also beomitted and the second laser-sensitive layer 4 shown in FIG. 5 a underthe reflection layer 5 r may be in the form of a laser-sensitiveadhesive layer.

In the case of the film in FIG. 5 b the layers occur in the followingsequence: carrier film 1, release layer 2, laser-sensitive layer 4,additional lacquer layer 5 c, reflection layer 5 r and adhesive layer 6.The layers 5 c and 6 can be of identical material or of differentmaterials. In this embodiment the laser-sensitive layer 4 is aprotective lacquer layer which is laser-sensitive insofar as it containsthe appropriate comparable pigments. A diffraction structure is formedin the mutually adjoining regions of the additional lacquer layer 5 c,the reflection layer 5 r and the adhesive layer 6. The diffractionstructure can be in the form of a diffraction grating. Alternatively thestructure 5 b may also be in the form of a hologram structure.

After the transfer film, in the present case a stamping film, has beenapplied to the substrate, the laser treatment is effected to producetransparent and/or colored markings in the laser-sensitive layer 4. Inorder to produce a given marking, preferably color marking, at a givenposition in the laser-sensitive layer 4, that location is irradiatedwith laser radiation.

In the case of the laser treatment of a film having the layer structureshown in FIG. 5 laser irradiation is effected through the reflectionlayer inclusive of the diffractive structure 5 b. The laser beam ispreferably directed perpendicularly on to the plane of the film fromabove. The reflection layer 5 r is transmissive in respect of the laserradiation, in particular when it is directed perpendicularly thereonto.The grating or hologram structure 5 b of the layer forming thereflection layer 5 r in the rest of the region is transmissive of thelaser radiation, but in this respect the radiation can also be reflectedmore or less and in part at the diffraction structure. Thelaser-sensitive layer 4 which is arranged under the layer forming thereflection layer 5 r in the rest of the region still within thediffraction structure 5 b and therebeneath is altered by the effect ofthe laser insofar as a change in color is produced by bleaching at thegiven location.

The bleaching operation as takes place in the illustrated embodiments inthe respective laser-sensitive layer is described hereinafter.

The laser-sensitive material of the laser-sensitive layer is a mixtureof three components, namely a cyan pigment component, a magenta pigmentcomponent and a yellow pigment component.

In the bleaching procedure, a blue or green or red color marking isproduced in a first step, insofar as that location is irradiated with agiven laser wavelength with which a given pigment component is bleached.

In order to produce the color blue only the yellow pigment component maybe bleached. Blue laser light is used for that purpose. A given minimumintensity is required for the bleaching operation. In addition a certainpulse duration may not be exceeded. In order to obtain a green colormarking in the first step only the magenta pigment component may bebleached. Green laser light is used for that purpose. In order to obtaina red marking in the first step only the cyan pigment component may bebleached. Red laser light is used for that purpose.

In order to produce a color marking of the color cyan or magenta oryellow at that location, that location is subjected to laser treatmentin a second step, more specifically with a laser wavelength with whichone of the pigment components which is not yet bleached at that locationis bleached. If a blue color marking has been produced in the firststep, the cyan pigment component and the magenta pigment component areunbleached at that location. In order to produce the color cyan at thatlocation the magenta pigment component must be bleached in this secondstep. That is effected with green laser light. That therefore produces acyan-colored marking at that location.

If a magenta-colored marking is to be obtained in that second stepinstead of the cyan-colored marking, the blue color marking produced inthe first step must be treated with red laser light. That causes thecyan pigment to be bleached at that location so that therefore themagenta pigment remains unbleached at that location. That thereforegives the magenta-colored marking at that location.

In a corresponding manner, a cyan-colored marking or a yellow-coloredmarking may be produced from a green color marking which was produced inthe first step and which is formed from unbleached cyan pigment andyellow pigment that has remained there, that operation being effectedmore specifically by treatment with blue laser light and red laser lightrespectively.

In a corresponding manner, a red color marking produced in the firststep can be converted in the second step into a yellow ormagenta-colored marking, more specifically by laser treatment in thesecond step with green laser light and blue laser light respectively.

In order to produce, at the location treated in the first and secondsteps, a transparent location, that is to say a white location if thebackground layer 5 is white, that location must be treated, in a thirdstep with a laser beam whose wavelength is so set that the pigmentcomponent which has remained unbleached at that location after thesecond step is bleached, that is to say the yellow color marking must bebleached with blue light, the magenta-colored marking with green lightand the cyan-colored marking with red laser light.

In the same manner, further adjacent locations are then treated in thelaser-sensitive layer 4 in order to produce further color markings inthe layer 4 of the stamping film. A full-color image can be produced inthat way.

Laser treatment can also be used to produce color markings or afull-color image in the coloring agent or agents in the laser-sensitivelayer by a color change. The laser treatment can be effected in acorresponding manner with successive process steps. Pigments fall to beconsidered as the coloring agents, that is to say color-impartingsubstances. They are mostly insoluble and they generally involveinorganic substances. However mostly soluble, organic coloring agentsare considered as the coloring agents. The color change is effected ineach case under specific laser conditions which are then applied in theindividual steps in the laser treatment.

The laser treatment of the transfer film for producing the colormarkings can also alternatively be effected prior to application of thefilm, more specifically in particular if the protective layer 3 is inthe form of a layer which is not or is only partially transparent forlaser radiation or a layer which is not transparent for laser radiationin the given wavelength range, or if there is provided an additionalUV-absorbent protective layer. The laser treatment is then effectedprior to application of the film by a procedure whereby the laser beamis directed on to the rear side of the film, that is to say on to thebackground layer 5 or the adhesive layer 6, and thus the laser-sensitivelayer 4 is therefore treated from the other side in order to produce thecolor markings therein in the same manner. The background layer 5 andthe adhesive layer 6 are transparent or at least partly transparent forthe laser radiation in question, in relation to such uses.

Color markings can also be produced in laminating films in acorresponding manner. Such laminating films are shown in FIGS. 6 through10. The laminating film in FIG. 6 includes a so-called overlay film 30,an optional intermediate layer 31, a laser-sensitive layer 40, anintermediate layer 50 which forms a background layer and which is alsooptional, and an adhesive layer 60 which is also optional. In thelaminating operation the laminating film is applied to the substratewith the adhesive layer 60 towards the surface of the substrate. Anadhesive bond to the surface of the substrate is produced by way of theadhesive layer 60. The overlay film 30 then forms the upper protectivelayer whose surface that is remote from the substrate forms the outersurface of the film. The overlay film 30 therefore remains applied thereafter application of the laminating film. It corresponds to theprotective layer 3 of the stamping film in FIG. 1. The laser-sensitivelayer 40 corresponds to the laser-sensitive layer 4, that is to say thefirst lacquer layer 4 of the stamping film in FIG. 1. The intermediatelayer 50 corresponds to the background layer 5, that is to say thesecond lacquer layer 5 of the stamping film in FIG. 1. The adhesivelayer 60 corresponds to the adhesive layer 6 of the stamping film inFIG. 1.

The laminating film in FIG. 6 a represents a modification of thelaminating film in FIG. 6, in which the background layer 50corresponding to the background layer 5 is missing, as in the hotstamping film in FIG. 1 c.

The laminating films in FIGS. 7 and 8 represent modifications of thelaminating film in FIG. 6, in which the background layer is modified ina corresponding manner to the background layer in the hot stamping filmsin FIGS. 2 and 3.

The laminating film in FIG. 9 involves a layer structure with a sequenceof the mutually superposed layers, which is modified in relation toFIGS. 6 through 8. The sequence of the layers corresponds to thestructure of the hot stamping film in FIG. 5. In this case the layer 70is an optional background layer.

FIG. 9 a shows an embodiment which is modified in comparison with theembodiment in FIG. 9, with a sequence of the layers corresponding to thestructure of the hot stamping film in FIG. 5 a.

The laminating film in FIG. 10 represents a modification of thelaminating film in FIG. 9. In this embodiment the overlay film 30 isprovided with a hot stamping film applied thereto. That hot stampingfilm applied at that location replaces the layers 31, 50 and 50 r, 40,70 and 60 which are provided in the laminating film in FIG. 9, by thecorresponding layers of the hot stamping film. In the case of the hotstamping film used for production of that laminating film, unlike thestamping film in FIG. 5, the reflection layer 5 r and thelaser-sensitive layer 4 are arranged in the reverse sequence so that, inthe case of the laminating film in FIG. 10, the reflection layer 5 r isnow arranged on the side of the laser-sensitive layer 4, which is remotefrom the substrate, in a corresponding manner to the laminating film inFIG. 9. In the same manner as in the other illustrated embodiments thediffraction structure 5 b in the laminating film in FIG. 10 is alsoprovided in the mutually adjoining regions of the layers 4 and 5. Inthis arrangement the lacquer layer 5 is in the form of a transparentlayer.

The laminating film in FIG. 10 a is of a similar structure to thelaminating film in FIG. 10. In the embodiment in FIG. 10 a however theoverlay film 30 is provided with a hot stamping film applied thereto,which is of a similar structure to the hot stamping film of theembodiment in FIG. 5 a. That hot stamping film which is applied to theoverlay film 30 replaces the layers 31, 40, 50, 50 r, 40, 70 and 60which are provided in the laminating film in FIG. 9 a, by thecorresponding layers of the hot stamping film. The laminating film inFIG. 10 a involves a series of layers in the following sequence: overlayfilm 30, adhesive layer 6, optional lacquer layer 5, laser-sensitivelayer 4, reflection layer 5 r, laser-sensitive layer 4, additionallacquer layer 5 c and protective layer 3. The laser-sensitive layers 4on both sides of the reflection layer 5 r can be identical, that is tosay the reflection layer 5 r is then arranged in that laser-sensitiveoverall layer. The laser-sensitive layers 4 however may also bedifferent. In that case the lacquer layer 5 is in the form of atransparent layer or a bright backup layer.

The laminating film in FIG. 10 b represents an embodiment in which a hotstamping film is also applied on the overlay film 30. That applied hotstamping film is of a similar configuration to the film in FIG. 5. Itreplaces the layers 31, 40, 50 and 50 r, 40, 70 and 60 respectivelyprovided in the laminating film in FIG. 9 a by the layers of the hotstamping film. The laminating film in FIG. 10 b has a series of layersinvolving the following sequence: overlay film 30, adhesive layer 6,optional lacquer layer 7, laser-sensitive layer 4, reflection layer 5 r,additional lacquer layer 5 c and protective layer 3. In this case thelacquer layer 7 is in the form of a transparent layer or a bright backuplayer.

The laser treatment of the laminating foil is implemented in acorresponding manner to that described for the transfer film, that is tosay by appropriate successive bleaching of the pigments or othercoloring agents contained in the laser-sensitive layer 40 or bycorresponding color changes of the pigments or other coloring agents.

The transfer films and laminating films with a film structure as aredescribed hereinbefore with reference to FIGS. 1 through 10 are appliedto a substrate comprising paper material with the described applicationprocedure. The substrate can preferably involve a card body which islaminated from a plurality of inlets, wherein the inlets at least partlycomprise paper material. Application of the films results in that casein respective multi-layer bodies which each have at least onelaser-sensitive layer 4 or 40 respectively. Color markings can beproduced in the laser-sensitive layer by the above-described lasertreatment. Embodiments by way of example of such multi-layer bodies withlaser-induced color markings are described hereinafter with respect toFIGS. 11 a, 11 b and 12 a, 12 b.

In the embodiment in FIGS. 11 a and 11 b a transfer film as shown inFIG. 1 a is applied to a substrate 8 comprising paper material. As canbe seen from the sectional view in FIG. 11 b the multi-layer bodycomprises the protective layer 3, the laser-sensitive layer 4, theadhesive layer 6 and the substrate 8, a special identification 81 beingpresent on the surface of the substrate 8. That identification 81 can bea separate layer applied to the substrate 8. As can be seen from theplan view in FIG. 11 a the identification 81 comprises variousidentification elements, more specifically a security print 81 d whichcan be in the form of guilloche patterns which are printed on, andfluorescent threads 81 f which preferably only fluoresce under UV lightand which in daylight can be seen as black threads. A watermark 81 w isalso provided in the substrate 8, as well as a security strip 81 s. Thesecurity strip 81 s can involve a body in the form of a strip or thread,which can have a diffraction and/or hologram structure and additionalsecurity features such as also for example laser-induced markings and soforth. A laser-induced image 10 y is produced in the laser-sensitivelayer, as can be seen from FIG. 11 a. That laser-induced image 10 y canbe produced in the form of a full-color image by way of theabove-described bleaching process. The laser-induced image 10 y isprovided only in a portion, which is rectangular in plan, of the surfaceof the card body 8. Preferably the entire transfer film can be appliedwith the laser-sensitive layer 4 exclusively in that region of the cardbody 8. As can be seen from FIG. 11 a the rectangular region of thelaser-induced image 10 y is transparent, that is to say the entireregion of the laser-sensitive layer is bleached by way of the lasertreatment in such a way that the colored image components aretransparent with color shading and the region around the color markingsis completely transparently bleached. That affords the advantage thatthe identification 81 on and in the card body 8 appears visibly throughthe laser-induced image 10 y. That affords a particularly high level ofsafeguard in respect of forgery.

In the modified embodiment in FIGS. 12 a and 12 b, a transfer film witha layer structure as shown in FIG. 1 is used, unlike the embodiment inFIGS. 11 a and 11 b. Therefore, in addition to the layers 3, 4, 6, ithas a background layer 5 between the laser-sensitive layer 4 and theadhesive layer 6. That background layer 5 is a layer which reflects thelaser radiation used in production of the laser-induced image 10 y andwhich does not pass through and absorbs the non-reflected component ofthe laser radiation. That special background layer provides that theidentification 81 under the laser-induced image 10 y is opticallycovered, that is to say for example with light in the visible spectralrange it is no longer perceptible from the outside. By virtue ofreflection of the light and possibly brightener substances additionallypresent in the background layer 5 the background layer 5 can provide forcolor boosting and/or brightening of the laser-induced color image 10 y.In addition the background layer 5 provides that, with the action of thelaser for producing the laser-induced image 10 y, the subjacent layers,that is to say in particular also the substrate 8, is not damaged bylaser irradiation or any other unwanted changes in the layers or in thesubstrate due to laser radiation do not occur.

FIGS. 13 through 15 show various multi-layer bodies formed by laminationof various overlay films 30 and inlets 90 comprising paper material. Allthese embodiments have at least one laser-sensitive layer 4. It isrespectively arranged in a laminating film which in regard to itsstructure substantially corresponds to the films which are shown inFIGS. 10, 10 a and 10 b and which involve laminating films produced byapplying a transfer film to an overlay film. In addition, theembodiments in FIGS. 14 and 15 have a further laser-sensitive layer inthe form of an overlay film 32 doped with carbon and/or carbon black.The film 32 is arranged beneath the overlay film 30 provided with thetransfer film. In the embodiment in FIG. 15 a background layer 5 isprovided between the laser-sensitive layer 4 and the doped overlay film32. The background layer 5 is comparable in respect of its configurationand function with the background layer 5 of the embodiment of FIGS. 12 aand 12 b.

1. A multi-layer body comprising a substrate and a single-layer ormulti-layer structure based on a transfer film with an adhesive layer,for example a hot stamping film, or a laminating film, wherein the layerstructure has at least one layer containing laser-sensitivematerial—referred to hereinafter as the laser-sensitive layer, and thelaser-sensitive material is such that a color marking or a black markingcan be produced by the action of laser in the laser-sensitive layer,wherein the substrate comprises a paper material and the laser-sensitivelayer is applied as part of the transfer film to the substratecomprising a paper material.
 2. A multi-layer body as set forth in claim1, wherein the laser-sensitive material is in the form of material whichis blackenable under the action of laser, preferably blackenable in grayscales, in particular in the form of carbon-doped and/or carbonblack-doped material.
 3. A multi-layer image as set forth in claim 1,wherein the laser-sensitive material has at least one coloring agentwhich is bleachable by the action of laser or which changes its color bythe action of laser with a color change.
 4. A multi-layer image as setforth in claim 3, wherein the laser-sensitive material is in the form ofa coloring agent mixture composed of a plurality of different coloringagent components, wherein it applies in respect of to at least two ofthe components that, under the laser conditions which are specific tothe one component, the other component is not or is substantially notchanged.
 5. A multi-layer body as set forth in claim 4, wherein thecoloring agent mixture is composed of at least three different coloringagent components, wherein each of the three coloring agent components isin the form of a pigment or other coloring agent and is bleachable bymeans of laser under laser conditions which are specific to therespective component, wherein it applies in respect to each of the threecomponents that, under the laser conditions which are specific to acomponent, the other components are not or are substantially notbleachable.
 6. A body as set forth in claim 4, wherein the laserconditions which are specific to the various components are differentpreferably in respect to the laser wavelength and, under the laserconditions which are specific to the respective component, the othercomponents are not or are substantially not bleachable.
 7. A body as setforth in claim 4, wherein at a location of the laser-sensitive layerpreferably at least in a region-wise manner at each location of thelaser-sensitive layer a plurality of different components of thecoloring agent mixture and preferably all various components of thecoloring agent mixture are arranged mixed and the color at that locationis formed by preferably subtractive color mixing.
 8. A body as set forthin claim 5, wherein the component absorbs light at the laser lightwavelength used for the bleaching operation insofar as at thatwavelength the component has an absorption maximum, preferably one of aplurality of absorption maxima or preferably its sole or its greatestabsorption maximum.
 9. A body as set forth in claim 5, wherein thecomponent absorbs light at the laser light wavelength used for thebleaching operation, but the component at that wavelength does not havean absorption maximum but said wavelength is outside the absorptionmaximum or outside the absorption maxima of the component.
 10. A body asset forth in claim 4, wherein the mixture has only three coloring agentcomponents or more than three coloring agent components.
 11. A body asset forth in claim 4, wherein a component is a cyan coloring agent,preferably cyan pigment, and/or that a component is a magenta coloringagent, preferably magenta pigment, and/or that a component is a yellowcoloring agent, preferably yellow pigment.
 12. A body as set forth inclaim 11, wherein the cyan coloring agent is in the form of a coloringagent which is bleachable exclusively or preferably with red laser lightand/or the magenta coloring agent is in the form of a coloring agentwhich is bleachable exclusively or preferably with green laser lightand/or the yellow coloring agent is in the form of a coloring agentwhich is bleachable exclusively or preferably with blue laser light. 13.A multi-layer body as set forth in claim 1, wherein provided between thelaser-sensitive layer and the substrate is a background layer which ispreferably reflecting to a high degree for the laser radiation whichacts upon laser irradiation of the laser-sensitive material and/or is inparticular non-transparent or substantially non-transparent and/orabsorbent for the non-reflected component of the laser radiation.
 14. Amulti-layer body as set forth in claim 13, wherein the background layeris transparent for light in the visible spectral range and/ortransparent or non-transparent for laser irradiation of only given laserconditions, in particular only given laser wavelengths, and ispreferably transparent or non-transparent for the laser radiation whichis used to produce a laser-induced marking in the laser-induced layer.15. A multi-layer body as set forth in claim 13, wherein the backgroundlayer is arranged exclusively in a region under the laser-sensitivelayer, preferably under the region in which the arrangement of thelaser-induced marking is provided.
 16. A process for the production of alaser-induced marking on or in a multi-layer body, wherein themulti-layer body is irradiated with laser radiation and in that case alaser-induced marking is produced by bleaching and/or color changeand/or blackening of the laser-sensitive material in the laser-sensitivelayer by the action of the laser radiation.
 17. A process as set forthin claim 16, wherein a multi-layer body with laser-sensitive materialwith two and preferably three bleachable components is usedcharacterized in that in a first step by laser irradiation of a locationof the laser-sensitive layer under laser conditions which are specificto one of the two, preferably three components, only the one componentis bleached and that in a second step by laser irradiation of the samelocation of the laser-sensitive layer under laser conditions which arespecific to a further one of the two, preferably three components, onlythat further component is bleached.
 18. A process as set forth in claim17, the process comprising a third step, wherein in the third step bylaser irradiation of the same location of the laser-sensitive layerunder laser conditions which are specific to another further one of thethree components at the same location of the laser-sensitive layer onlysaid other further component is bleached.
 19. A process as set forth inclaim 17, the process comprising an n-th step, wherein in the n-th stepby laser treatment of the same location of the laser-sensitive layerunder laser conditions which are specific to an n-th further componentonly said n-th component is bleached, wherein n is greater than
 3. 20. Aprocess as set forth in claim 17, wherein all components are bleached bythe laser irradiations of said location of the laser-sensitive layer.21. A process as set forth in claim 16, wherein the degree of bleachingto be achieved is adjusted in the laser irradiation operation by controlof the laser conditions, in particular the laser intensity and/or thepulse duration and/or the irradiation time.
 22. A process as set forthin claim 16, wherein at least one of the components has a color changein the laser irradiation operation.
 23. A process a set forth in claim16, wherein the laser-sensitive layer is laser-irradiated successivelyat a plurality of locations.
 24. A process a set forth in claim 16,wherein at the one location of the laser-sensitive layer a plurality ofdifferent components and preferably all different components arearranged mixed and the color of said location is formed by subtractivecolor mixing.
 25. A process a set forth in claim 16, wherein a cyancoloring agent, preferably cyan pigment, and/or a magenta coloringagent, preferably magenta pigment, and/or a yellow coloring agent,preferably yellow pigment, is used as the component.
 26. A process a setforth in claim 25, wherein red laser light is used for bleaching thecyan coloring agent and/or green laser light is used for bleaching themagenta coloring agent and/or blue laser light is used for bleaching theyellow coloring agent.
 27. A process as set forth in claim 25, whereinthe color blue is formed by superimposition, preferably subtractivemixing of the colors cyan and magenta, preferably from the coloringagent mixture with cyan coloring agent, magenta coloring agent andyellow coloring agent by bleaching of the yellow coloring agent; and/orthe color green is formed by superimposition, preferably subtractivemixing of the colors cyan and yellow, preferably from the coloring agentmixture with cyan coloring agent, magenta coloring agent and yellowcoloring agent by bleaching of the magenta coloring agent; and/or thecolor red is formed by superimposition, preferably subtractive mixing ofthe colors yellow and magenta, preferably from the coloring agentmixture with magenta coloring agent, yellow coloring agent and cyancoloring agent by bleaching of the cyan coloring agent; and/or black orgray is formed by superimposition, preferably subtractive mixing of thecolors cyan, magenta and yellow, preferably from the coloring agentmixture with magenta coloring agent, yellow coloring agent and cyancoloring agent; and/or the color magenta is formed by the magentacoloring agent by bleaching of the coloring agents present in thecoloring agent mixture apart from the magenta coloring agent, preferablyfrom the coloring agent mixture including magenta coloring agent, yellowcoloring agent and cyan coloring agent, by bleaching of the yellowcoloring agent and the cyan coloring agent; and/or the color cyan isformed by the cyan coloring agent by bleaching of the other coloringagents present in the coloring agent mixture apart from the cyancoloring agent, preferably from the coloring agent mixture includingcyan coloring agent, yellow coloring agent and magenta coloring agent,by bleaching of the magenta coloring agent and the yellow coloringagent; and/or the color yellow is formed by the yellow coloring agent bybleaching of all coloring agents present in the coloring agent mixtureapart from the yellow coloring agent, preferably from the coloring agentmixture including yellow coloring agent, magenta coloring agent and cyancoloring agent, by bleaching of the magenta coloring agent and the cyancoloring agent.